1. Field of the Invention
The present invention relates to a tool system and method for cleaning out restrictions located substantially downhole in oil wells and the like, and more particularly to a tool system for cleaning out the zone below a packer without the need for removing the packer, utilizing a tool which has a relatively small diameter, less than the diameter of the production tubing, but having radially extendable cleaning blades which are expanded out after the tool is longitudinally moved through the production tubing and located down below the packer. The zone below the packer to be cleaned out is filled with debris restricting flow from the zone to the interior of the production tubing, and the tool system of the invention in its expanded configuration rotated about its longitudinal axis, moving the blade within the zone to loosen the debris, which is then removed by fluid circulation. Additionally, the present invention relates to such a tool having a replaceable blade set allowing for the same tool to be used for different diameter casings.
2. Prior Art and General Background
Following drilling operations for an oil or gas well, a string of steel casing is installed into the well bore to isolate the producing interval or zone from other formations. A string of steel production tubing is installed longitudinally inside the casing with a packer set above the production perforations, and the well is produced through the production tubing. Often times a sand screen is set opposite the production perforations to restrict entry of sand grains from unconsolidated sandstone formations into the casing and tubing. In the event this precautionary measure is inadequate, or for other reasons, which may exist over a period of time, such as scale, corrosion, etc., flow from the well may become restricted or cease, requiring clean-out of the debris in the zone below the packer.
The usual procedure to resolve this problem has been to employ a workover rig, kill the well with weighted drilling fluids, retrieve the tubing and packer, and clean out the restriction or debris. This operation is considerably expensive, especially when the tubing and packer cannot be easily retrieved.
In general it would not be suitable to use apparatus for severing well casing such as described in Smith, U.S. Pat. No. 3,378,072 issued on Apr. 16, 1968, as the apparatus was not intended to be made in a size small enough to be lowered through the interior of a production tubing string, which is generally in the neighborhood of 21/2-41/2 inches, and the apparatus would, in any event, sever the casing and would not be suitable for movement of the blade longitudinally along the axis of the casing while the blade is rotated. For other examples of apparatus for severing well casing, see for example U.S. Pat. Nos. 4,068,711 (issued 01/17/78 to Aulenbacher); 2,328,782 (issued 09/07/43 to P. T. Bynum); 2,284,211 (issued 05/26/42 to G. E. Justice); and Re. 21,824 (issued 06/10/41 to G. A. Lowrey).
3. General Discussion of the Invention
In contrast the present invention relates to a special tool and method of accomplishing the same results by employing a small hydraulically driven clean-out tool that is conveyed on small diameter tubing down through the production tubing and packer. This smaller tubing requires lighter, less expensive hoisting equipment and obviates the need for any fishing operations, since the production tubing and packer remain in place.
Also, the operation can be conducted under pressure without killing the well, by employing small tubing, hydraulic snubbing or coil tubing hoisting equipment and a down-hole motor (e.g., a "Dynadril" motor).
The present invention is designed to clean out the smaller inside diameter of the producting tubing as the tool is lowered, and then, after the tool has been positioned below the packer, expand the tool, by for example pivoting out a set of clean-out blades, and cleaning out the larger, inside diameter of the casing by rotating the expanded tool. It is noted that in no way is the tool of the invention designed to cut, penetrate or remove the casing wall or enlarge any open hole section of the well bore.
Thus, the present invention is able to clean out all the restricting formations without the need for removing the packer or the production tubing and to do so with a relatively inexpensive, flexible and highly reliable tool and method.
Additionally, the tool is preferably supplied with a series of differently configured, pivotable clean-out blade sets, so that the same tool body and related equipment can be used for different diameter casings. The difference in configuration of the blade sets is of primary importance at the upper ends, as their degree of bias or angularity will determine the outwardly pivoted disposition and hence their effective clean-out diameter as the tool is rotated. Additionally such configuration insures that, for a particular diameter casing, the clean-out blades will not cuttingly engage the inside surface of the casing and effectively limits the radial expansion of the tool.
It is therefore an object of the present invention to provide a new method and apparatus suitable for loosening the debris in an isolated zone below a packer which will not require the removal of the packer or the production tubing.
It is further an object of the present invention that the method and apparatus of the present invention allow circulation downward through the tubing string into the zone for circulating the debris out of the zone.